The present invention relates generally to optical switches, and more particularly to a thermorefractive optical switch utilizing temperature dependence of the refraction index of certain liquids to filter invasive radiation over a wide spectral band.
Prior art optical switches may generally be classified as mechanical, electromechanical, electro-optical, magneto-optical, and acousto-optical in principle of operation. These switches exhibit certain disadvantages for general application. For example, mechanical and electromechanical switches have moving parts and may have lower reliability of operation than the other types. Magneto-optic switches generally require an electromagnet for generating a magnetic field. Electro-optic switches require relatively high voltages for operation and may be polarization sensitive. Acousto-optic switches require a medium which supports the propagation of acoustic energy and usually are characterized by small permissible changes in refractive index.
The invention solves or substantially reduces in critical importance problems with prior art devices as just mentioned by providing a passive thermorefractive optical switching device comprising a substrate of light absorbent matrix material and includes an array of a plurality of holes filled with liquid having an index of refraction which is highly temperature dependent. Under normal operating conditions (i.e. to about 80.degree. C.), a difference in refractive index between the liquid and the matrix material confines incident light to propagation along the waveguide defined by the liquid filled holes. As the temperature of the liquid is raised as by heating by incident light radiation or otherwise, the refractive index of the liquid decreases sufficiently, especially near boiling, to promote light leakage from the liquid to the matrix material.
The invention may find substantial utility for optical switching devices, as a spatial light modulator for use with incoherent light, as a remote temperature sensor or other optical switching application.
It is therefore a principal object of the invention to provide an improved optical switch.
It is a further object of the invention to provide a thermorefractive optical switch based on temperature dependence of the phase change of a liquid in conjunction with a structured matrix.
It is a further object of the invention to provide a passive optical switch for protecting sensitive optical systems from invasive light radiation.
These and other objects of the invention will become apparent as a detailed description of the representative embodiments proceeds.